The rules of Mathdoku are based on the rules of Sudoku. This is an example Mathdoku starting grid.
A completed Mathdoku grid is like a Sudoku in that each row and column must contain the numbers 1-6 once and only once (notice that this grid is smaller than the standard Sudoku grid).
In addition, the grid is split up in to multiple sections, typically between two and four cells. Each section has a number and a Mathematical operator. You must make that number using the Mathematical operator.
As an example, our section in the top-left has four cells, with a constraint of '24*'. This means when we multiply our four numbers together, they must make 24.
Mathdoku puzzles are different in that a number can be repeated in each section, so our numbers in this instance could be 1*2*2*6=24, arranged in any order in those four cells.
Remember that each number can only appear once in each row/column, so there are restrictions on how the two '2' numbers can appear. Namely, they have to be on a diagonal
The rules really are simpler once you start to attempt to solve a puzzle, look at Mathdoku techniques.